Gene expression of the IGF binding proteins during post-implantation embryogenesis of the mouse; comparison with the expression of IGF-I and -II and their receptors in rodent and human

The IGF binding proteins (IGFBPs) comprise at least six distinct species which may modulate the action of IGFs. IGFs are important regulators of fetal growth and differentiation. We have studied the mRNA expression of the six IGFBPs during post-implantation embryogenesis (day 11-18) by in situ hybridization techniques. Expression of IGFBP-1 was detected in mouse conceptuses after day 12 of gestation and seemed restricted to the liver. Transcripts for IGFBP-2, -4 and -5 were detected in various tissues and were found in all stages tested. In contrast, expression of IGFBP-3 and -6 could be detected only weakly in late gestational embryos. Comparison of the expression pattern of IGFBP-2, -4 and -5, which were found widely distributed in mouse conceptuses, revealed that IGFBP-2 was expressed mainly in the ectodermal layer and also in the mesoderm derived part of the tongue (day 13.5). Transcripts for IGFBP-4 however, only were detected in the mesoderm derived tissues, whereas expression of IGFBP-5 was restricted to the ectodermal layer. A similar distribution pattern was observed in the lung. In general, expression of IGFBP-2 and -5 was detected in the same cells, whereas IGFBP-4 and -5 were expressed mainly in different cell types. In rodents as in the human there is widespread expression of the genes coding IGFs, the IGFBPs and the receptors during pre- and postimplantation embryogenesis. These data support the assumption that the IGFs play an important role during embryogenesis.</p

Macrophage-mediated gliadin degradation and concomitant IL-27 production drive IL-10- and IFN-γ 3-secreting Tr1-like-cell differentiation in a murine model for gluten tolerance

Celiac disease is caused by inflammatory T-cell responses against the insoluble dietary protein gliadin. We have shown that, in humanized mice, oral tolerance to deamidated chymotrypsin-digested gliadin (CT-TG2-gliadin) is driven by tolerogenic interferon (IFN)-γ 3- and interleukin (IL)-10-secreting type 1 regulatory T-like cells (Tr1-like cells) generated in the spleen but not in the mesenteric lymph nodes. We aimed to uncover the mechanisms underlying gliadin-specific Tr1-like-cell differentiation and hypothesized that proteolytic gliadin degradation by splenic macrophages is a decisive step in this process. In vivo depletion of macrophages caused reduced differentiation of splenic IFN-γ 3- and IL-10-producing Tr1-like cells after CT-TG2-gliadin but not gliadin peptide feed. Splenic macrophages, rather than dendritic cells, constitutively expressed increased mRNA levels of the endopeptidase Cathepsin D; macrophage depletion significantly reduced splenic Cathepsin D expression in vivo and Cathepsin D efficiently degraded recombinant γ 3-gliadin in vitro. In response to CT-TG2-gliadin uptake, macrophages enhanced the expression of Il27p28, a cytokine that favored differentiation of gliadin-specific Tr1-like cells in vitro, and was previously reported to increase Cathepsin D activity. Conversely, IL-27 neutralization in vivo inhibited splenic IFN-γ 3- and IL-10-secreting Tr1-like-cell differentiation after CT-TG2-gliadin feed. Our data infer that endopeptidase mediated gliadin degradation by macrophages and concomitant IL-27 production drive differentiation of splenic gliadin-specific Tr1-like cells